;==============================================================
; Region detector
; Returns a=1 for Japanese, 0 for export
; Based on code found in many Sega games (eg. Super Tennis)
;==============================================================
IsJapanese:
    ld a,%11110101  ; Output 1s on both TH lines
    out ($3f),a
    in a,($dd)
    and %11000000  ; See what the TH inputs are
    cp %11000000  ; If the input does not match the output then it's a Japanese system
    jp nz,_IsJap

    ld a,%01010101  ; Output 0s on both TH lines
    out ($3f),a
    in a,($dd)
    and %11000000  ; See what the TH inputs are
    jp nz,_IsJap    ; If the input does not match the output then it's a Japanese system

    ld a,%11111111  ; Set everything back to being inputs
    out ($3f),a

    ld a,0
    ret

_IsJap:
    ld a,1
    ret